I have a Excel addin written in VBA which iterates through used range of a sheet and manipulates cell values. Its a simple addin but now user requirements have changed and I want to develop it in C# in Visual studio. For this purpose i was looking into VSTO but as far as i can understand in visual studio you can develop addin for a single version of excel. I have to give support for excel 2010 and excel 2013. What should I do to overcome this issue. which visual studio version i should use?
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Any version of Visual Studio from 2010 to the present should be able to create VSTO Add-ins for Excel 2010. From VS 2012 onwards, also for Office 2013. Which set of templates you see in the later versions depends on 1) the version of Office installed and 2) the version of the .NET Framework selected when creating the project (4.0 for 2010; 4.5 for later). More information can be found on this page: https://blogs.msdn.microsoft.com/vsto/2013/03/06/office-developer-tools-for-visual-studio-2012-now-available-with-office-2013-and-net-framework-4-5-support/
Note that you should have only one version of Office installed in the development environment.
If possible, you should develop the Add-in for Excel 2010. An Add-in developed for an older version will run for a newer version, without you needing to do anything in addition - assuming Microsoft hasn't made changes to the parts of the object model you use which will "break" it. Since Microsoft pays special attention to backwards compatibility, this is usually not a problem, but thorough testing is important. It is not necessary to re-build or otherwise change the installation for installing to a newer version of Office.
One important reason to develop against the older version is that forwards compatibility is not supported. In other words, if you should use something in the newer version that's not present in the older one, that code will fail.
Also, the VSTO functionality will automatically "re-map" references made to an older set of PIAs to the newer ones for a newer version of Office. The reverse is not the case.
If for some reason it's not possible to program using the older version, as long as you have the .NET Framework 4.0 (or later) you can use the "Embed Interop types" property of a Reference to embed the PIA information in your project, so that it travels with your solution instead of referencing the PIAs installed in the GAC and makes them version independent. This is fine, in theory, but requires very thorough and careful testing since - besides the forwards compatibility problem - the actual information embedded does not always behave correctly.
